This invention relates to an image display device which combines two or more images for display. More particularly it relates to a multi-projection image display device which combines images projected from a plurality of projection type display units to form one picture on a screen, and concerns a device or method which is capable of smoothing the seams between images.
In combining several images, for example, using a multi-projector device composed of a plurality of projectors, it is ideal when the seams between images projected from neighboring projectors can be so smoothly joined as to look invisible, forming one picture (or pictures) on a screen.
Conventionally, the method as disclosed in Japanese Patent Prepublication No. 94974/96 has been employed to realize this objective. For example, to prevent the projection range of each projector on the screen from overlapping that of an adjacent projector, a shielding plate is installed in the border between neighboring image projection ranges perpendicularly to the screen in such a way that light from one projector does not enter the projection range of the light of an adjacent projector. In addition, transmission type screens with different polarization characteristics are provided between neighboring projection ranges so that light from adjacent projectors cannot reach the viewer physically.
In the above mentioned optical method for combining neighboring images, however, it is necessary to physically define the image projection range of each projector beforehand. This necessitates adjustment of projectors so that the projected image precisely coincides with the defined projection range. This adjustment includes adjusting the projector angle and the internal optical system of each projector, or in case of cathode-ray tube type projectors, adjusting deflecting voltage waveforms to reshape the projected images.
However, in case of liquid crystal projectors, the reshaping of projected images is not so easy as in the case of cathode-ray tube type projectors and only optical adjustments are used to change the image projection position and shape, though the freedom of adjustment is limited.
These adjustment methods are not only troublesome, but they also need frequent readjustments because optimum adjustment levels easily vary with variation in the temperature and the magnetic field in the room in which the adjusted projectors are installed. Therefore, when the conventional methods are used, it is very difficult to display on a screen a whole picture (or pictures) composed of several images with smooth seams.
Also, installation of shielding plates on the screen might unfavorably affect the uniformity of the screen itself, which might be reflected in the projected images, so that a smoothly joined picture can not be obtained.
The main object of the this invention is to solve the above-mentioned in a way that problem. Eliminates the need for a special screen structure for prevention of penetration of light from adjacent projectors, as well as precise optical adjustment of projectors, while realizing smoothly joined images in which the seams are not conspicuous. According to the invention, even image projection by projectors can be made by image signal processing.
To achieve the above stated object, the invention has the following structure.
According to the invention, adjustment is made on overlapping parts (signals) of several images on a projection surface (for example, a screen). Specifically, in terms of image signals supplied to projectors which project images from the back or front of the screen, a partial image area to be dealt with by each projector is cut out to generate a corresponding image signal, which is processed to perform reshaping or geometric transformation of the projected image and local color correction. This process may be implemented using either hardware or software.
In addition, the invention is characterized in that, as an image display method employed in a multi-projection image display device provided with a plurality of image output units, on a display screen which displays images projected from said image output units, the image projection area of one of said image output units overlaps that of another image output unit, and said image output unit and said other image output unit deliver mutually correlated. images to the image overlap area.
Here, a control parameter to be used for the geometric transformation and color correction may be generated as follows: the image signal for a desired image pattern is supplied to each projector, the state of the projected image on the screen is read and the control parameter is calculated from the image state data thus read.
For each projector, which is in charge of an image projection range adjacent to another image projection range, it is desirable to set its position, angle and optical system so that its maximum image projection range on the screen overlaps that of the adjacent maximum image projection range by a few percent in the border. The areas where neighboring maximum image projection ranges overlap each other are areas where the images projected from the respective neighboring projectors in charge of these projection ranges are optically added or integrated. The state of the image projection on the screen as a result of this optical image addition is read and the read image data is used to calculate control parameters to make an optical image addition model, and this model is used to obtain necessary control parameters for geometric transformation and local color correction of the supplied images (signals) so that smooth connection of neighboring images can be made as a result of optical image addition. According to the obtained geometric transformation and local color correction parameters, image geometric transformation and local color correction are carried out and the processed image signals are supplied to the projectors.
The invention constitutes a multi-projection image display device to form one or more pictures on a screen, characterized in that image projectors which project images on said screen and a control unit which, when the image projection display range on said screen of one of the projectors has an area which overlaps that of another projector, enables said projector and said other projector to output mutually correlated images to said overlap area on said screen.
The invention also includes a computer readable storage medium which stores a program to ensure that, on a screen where image output units display images, the image display range of one of said image output units and that of another image output unit partially overlap, and that said image output unit and said other image output unit output mutually correlated images. The invention also constitutes an image signal regenerator which comprises storage media to store image data in divided form for the respective image output units, so that said image output unit and said other image output unit can output mutually correlated images to the area where images from the image output units overlap; and image signal supply units which supply image signals based on image data read from said storage media.
The invention eliminates the need for readjustments of components, such as the screen and projectors, because it only needs adjustments relating to image overlap areas. Specifically, it involves making an optical image addition model, depending on the conditions of the screen, projectors and other components, and using the model to obtain a solution; as a result, components such as the screen and projectors need not be readjusted as far as an optical image addition model which has a solution can be obtained.